code: def _random_grid(n, m=None, seed=123):
      if m is None:
          m = n
      prg = np.random.RandomState(seed)
      g = prg.uniform(size=n * m)
      x, y = np.meshgrid(range(n), range(m))
      return pd.DataFrame({"x": x.ravel(), "y": y.ravel(), "g": g})
  
file_path: plotnine/tests/test_geom_raster.py
imports: import numpy
  import pandas
  import pytest
  from plotnine import aes, geom_raster, ggplot
  from plotnine.exceptions import PlotnineWarning
label_desc: Use image node_id 1 for calling a global function with example usage: _random_grid(n, m, seed) and returns: pd